Chimneys that are one brick thick and unlined are a fire hazard and must be reported. A two-brick chimney, without a flue liner is acceptable as long as the mortar and bricks are in good condition. Metal flues for gas appliances such as furnaces must have a cap on them to prevent weather and animals from entering.  Caps on masonry chimneys are cement/mortar and have a tendency to crack. (Additional brick chimney conditions and concerns are outlined under masonry chimneys.)

 

Brick Problems in Chimneys 

• Spalling brick.  Spalling occurs when moisture gets into the brick and freezes.  This causes the surface of the brick to fall off.  The porosity and quality of the brick, and the climate have a significant impact on spalling.

• Deteriorating brick.  This is usually a softer clay salmon brick that is designed for use on the inside of an 8-inch thick wall. The deterioration is more complete than the spalling brick.  It is relatively easy to recognize due to its orange color.